Modelling of the Quantum Transport in Strained Si/SiGe/Si Superlattices Based P-i-n Infrared Photodetectors for 1.3 - 1.55 μm Optical Communication

In this paper, a p-i-n heterojunction based on strain-compensated Si/Si1-xGex/Si multiple quantum wells on relaxed Si1-yGey is proposed for photodetection applications. The Si1-yGey/Si/Si1-xGex/Si/Si1-yGey stack consists in a W-like potential profile strain-compensated in the two low absorption windows of silica fibers infrared (IR) photodetectors. These computations have been used for the study of p-i-n infrared photodetectors operating at room temperature (RT) in the range 1.3 - 1.55 μm. The electron transport in the Si/Si1-xGex/Si multi-quantum wells-based p-i-n structure was analyzed and numerically simulated taking into account tunneling process and thermally activated transfer through the barriers mainly. These processes were modeled with a system of Schrodinger and kinetic equations self-consistently resolved with the Poisson equation. Temperature dependence of zero-bias resistance area product (RoA) and bias-dependent dynamic resistance of the diode have been analyzed in details to investigate the contribution of dark current mechanisms which reduce the electrical performances of the diode.

Organic Thin Film Transistors Based on Distyryl-Oligothiophenes: Role of AFM Images in Analyses of Charge Transport Properties

Significant advances have been made recently in the area of organic electronics and optoelectronics based on small molecules as a result of an improved chemistry and a better technology. Together with light emitting diodes and solar cells, transistors are among the most studied components. The development of new semiconductors induced a real improvement in organic thin film transistor’s performances. Additionally, the synthesis of new soluble and air-stable molecules with the ability to process the active materials at low temperatures over large areas on substrates such as plastic or paper provide unique technologies and generate new applications. However the control of the solid state structure has emerged as essential to realize the full intrinsic potential that organic semiconductors possess. Atomic force microscopy (AFM) was likely to contribute to a further advancement of knowledge. The ability of the AFM to produce three dimensional maps at the micro- and nanometer scale has greatly increased its popularity as an imaging tool. Recently, distyryl-oligothiophenes and their derivatives appear as a new class of molecular semiconductors. Detailed morphological studies of organic active layers based on such new semiconductors involved in organic thin film transistors (OTFTs) have brought a large knowledge about the impact of chemical and physico-chemical aspects on charge transport efficiency.

Preliminary Study on the Magnetic Properties of GeMn Nanocolumn/Ge Multilayers

Ge0.94Mn0.06 nanocolumn thin film is a unique phase of GeMn diluted magnetic semiconductors (DMS) which exhibit Curie temperature (TC) > 400 K. The multilayers of Ge0.94Mn0.06 nanocolumns separated by nano-scaled spacers represent great interests for spintronic applications, such as spin valves or giant magneto-resistance (GMR) multilayers. In this article, we present the results obtained from the preliminary study on the exchange coupling in two types of GeMn nanocolumn/Ge multilayers. All the samples have been grown using molecular beam epitaxy (MBE). The superconducting quantum interference device (SQUID) magnetometer has been used to determine the magnetic properties of the samples. In the multilayer system Ge/[Ge0.94Mn0.06(40 nm)/Ge(d nm)]9/Ge0.94Mn0.06(40 nm)/Ge, no exchange coupling can be observed. Inversely, exchange coupling between the layers exists and depends on the thickness of the Ge spacers for the GeMn nanocolumns/Ge multilayer spin valve systems. The exchange coupling in the nanocolumns multilayer systems has been shown to be complex due to the leakage field induced by neighboring nanocolumns and the magnetic anisotropy of nanocolumns.

具有抗癌活性的新型三氮唑核苷类似物的研究进展

核苷类似物是一类重要的抗癌药物。通过在非天然核苷的三氮唑碱基中引入芳香基团,笔者发展了一系列1,2,4-三氮唑核苷类似物。该文简要综述这些三氮唑核苷类似物的分子设计、化学合成及其抗癌活性测试的研究成果。

Therapeutic siRNA:state of the art

RNA interference(RNAi)is an ancient biological mechanism used to defend against external invasion.It theoretically can silence any disease-related genes in a sequence-specific manner,making small interfering RNA(siRNA)a promising therapeutic modality.After a two-decade journey from its discovery,two approvals of siRNA therapeutics,ONPATTRO®(patisiran)and GIVLAARI™(givosiran),have been achieved by Alnylam Pharmaceuticals.Reviewing the long-term pharmaceutical history of human beings,siRNA therapy currently has set up an extraordinary milestone,as it has already changed and will continue to change the treatment and management of human diseases.It can be administered quarterly,even twice-yearly,to achieve therapeutic effects,which is not the case for small molecules and antibodies.The drug development process was extremely hard,aiming to surmount complex obstacles,such as how to efficiently and safely deliver siRNAs to desired tissues and cells and how to enhance the performance of siRNAs with respect to their activity,stability,specificity and potential off-target effects.In this review,the evolution of siRNA chemical modifications and their biomedical performance are comprehensively reviewed.All clinically explored and commercialized siRNA delivery platforms,including the GalNAc(N-acetylgalactosamine)–siRNA conjugate,and their fundamental design principles are thoroughly discussed.The latest progress in siRNA therapeutic development is also summarized.This review provides a comprehensive view and roadmap for general readers working in the field.

Amphiphilic Dendrimer Vectors for RNA Delivery:State-of-the-Art and Future

Dendrimers,a special family of polymers,are particularly promising materials for various biomedical applications by virtue of their well-defined dendritic structure and cooperative multivalency.Specifically,in this Account,we present state-of-the-art amphiphilic dendrimers for nucleic acid delivery.Ribonucleic acid(RNA)molecules are fast becoming an important drug modality,particularly since the recent success of mRNA vaccines against COVID-19.Notably,RNA therapeutics offer the unique opportunity to treat diseases at the gene level and address“undruggable”targets.However,RNA therapeutics are not stable and have poor bioavailability,imposing the need for their protection and safe delivery by vectors to the sites-of-action to allow the desired therapeutic effects.Currently,the two most advanced nonviral vectors are based on lipids and polymers,with lipid vectors primarily exploiting the membrane-fusion mechanism and polymer vectors mainly endocytosis-mediated delivery.Notably,only lipid vectors have been advanced through to their clinical use in the delivery of,for example,the first siRNA drug and the first mRNA vaccine.The success of lipid vectors for RNA delivery has motivated research for further innovative materials as delivery vectors.Specifically,we have pioneered lipid/dendrimer conjugates,referred to as amphiphilic dendrimers,for siRNA delivery with the view to harnessing the delivery advantages of both lipid and polymer vectors while enjoying the unique structural features of dendrimers.These amphiphilic dendrimer vectors are lipid/dendrimer hybrids and are thus able to mimic lipid vectors and exploit membranefusion-mediated delivery,while simultaneously retaining the multivalent properties of polymer vectors that allow endocytosis-based delivery.In addition,they have precisely controllable and stable nanosized chemical structures and offer nanotechnology-based delivery.Effective amphiphilic dendrimer vectors share two important elements:chemical hydrophilic entities to bind RNA and RNA complex-stabilizing hydrophobicity.These two combined features allow the encapsulation of RNA within a stable complex before its release into the cytosol following endocytosis.This hydrophilic/hydrophobic balance permitted by the structural features of amphiphilic dendrimers plays a determining role in RNA delivery success.In this Account,we provide a conceptual overview of this exciting field with the latest breakthroughs and key advances in the design of amphiphilic dendrimers for the delivery of siRNA and mRNA.Specifically,we start with a short introduction to siRNA-and mRNA-based therapeutics and their delivery challenges.We then outline the pioneering and representative studies on amphiphilic dendrimer vectors to highlight their historical development and promising features that offer to facilitate the once challenging RNA delivery.We conclude by offering perspectives for the future of amphiphilic dendrimer vectors for nucleic acid delivery in general.

On-surface synthesis of covalent coordination polymers on micrometer scale

在表面上合成在下面超离频真空提供有希望的策略在原子水平控制物质，与为有显著电子、磁性，或催化的性质的新二维的材料的设计的重要含意。这策略必须由于共有原子价契约的不可逆的性质处理领域的有限扩展的问题，它阻止缺点成熟。我们这里证明扩大材料能被一个控制共淀积过程生产。特别地，有 Ag (111 ) 表面上的铁原子的 quinoid 两性离子分子的共淀积在 570 点认为 K 基于共有原子价协作契约允许测微计大小的领域的形成。这个工作开创测微计规模的构造在真空条件下面的单个层的共有原子价协作材料。

An ionizable supramolecular dendrimer nanosystem for effective siRNA delivery with a favorable safety profile

Gene therapy using small interfering RNA(siRNA)is emerging as a novel therapeutic approach to treat various diseases.However,safe and efficient siRNA delivery still constitutes the major obstacle for clinical implementation of siRNA therapeutics.Here we report an ionizable supramolecular dendrimer vector,formed via self-assembly of a small amphiphilic dendrimer,as an effective siRNA delivery system with a favorable safety profile.By virtue of the ionizable tertiary amine terminals,the supramolecular dendrimer has a low positively charged surface potential and no notable cytotoxicity at physiological pH.Nonetheless,this ionizable feature imparted sufficient surface charge to the supramolecular dendrimer to enable formation of a stable complex with siRNA via electrostatic interactions.The resulting siRNA/dendrimer delivery system had a surface charge that was neither neutral,thus avoiding aggregation,nor too high,thus avoiding cytotoxicity,but was sufficient for favorable cellular uptake and endosomal release of the siRNA.When tested in different cancer cell lines and patient-derived cancer organoids,this dendrimer-mediated siRNA delivery system effectively silenced the oncogenes Myc and Akt2 with a potent antiproliferative effect,outperforming the gold standard vector,Lipofectamine 2000.Therefore,this ionizable supramolecular dendrimer represents a promising vector for siRNA delivery.The concept of supramolecular dendrimer nanovectors via self-assembly is new,yet easy to implement in practice,offering a new perspective for supramolecular chemistry in biomedical applications.

Automated calculation and convergence of defect transport tensors

Defect diffusion is a key process in materials science and catalysis,but as migration mechanisms are often too complex to enumerate a priori,calculation of transport tensors typically have no measure of convergence and require significant end-user intervention.These two bottlenecks prevent high-throughput implementations essential to propagate model-form uncertainty from interatomic interactions to predictive simulations.In order to address these issues,we extend a massively parallel accelerated sampling scheme,autonomously controlled by Bayesian estimators of statewide sampling completeness,to build atomistic kinetic Monte Carlo models on a state-space irreducible under exchange and space group symmetries.Focusing on isolated defects,we derive analytic expressions for drift and diffusion coefficients,providing a convergence metric by calculating the Kullback–Leibler divergence across the ensemble of diffusion processes consistent with the sampling uncertainty.The autonomy and efficacy of the method is demonstrated on surface trimers in tungsten and Hexa-interstitials in magnesium oxide,both of which exhibit complex,correlated migration mechanisms.

Density Functional Theory and Tight Binding-Based Dynamical Studies of Carbon Metal Systems of Relevance to Carbon Nanotube Growth

Density functional theory(DFT)and tight binding(TB)models have been used to study systems containing single-walled carbon nanotubes(SWNTs)and metal clusters that are of relevance to SWNT growth and regrowth.In particular,TB-based Monte Carlo(TBMC)simulations at 1000 or 1500 K show that Ni atoms that are initially on the surface of the SWNT or that are clustered near the SWNT end diffuse to the nanotube end so that virtually none of the Ni atoms are located inside the nanotube.This occurs,in part,due to the lowering of the Ni atom energies when they retract from the SWNT to the interior of the cluster.Aggregation of the atoms at the SWNT end does not change the chirality within the simulation time,which supports the application of SWNT regrowth(seeded growth)as a potential route for chirality-controlled SWNT production.DFT-based geometry optimisation and direct dynamics at 2000 K show that Cr and Mo atoms in Cr5Co50 and Mo5Co50 clusters prefer to be distributed in the interior of the clusters.Extension of these calculations should deepen our understanding of the role of the various alloy components in SWNT growth.